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<H1>ac_eq(?X, ?Y, ++C)</H1>
Arc-consistent implementation of X #= Y + C.
<DL>
<DT><EM>X</EM></DT>
<DD>Variable or integer
</DD>
<DT><EM>Y</EM></DT>
<DD>Variable or integer
</DD>
<DT><EM>C</EM></DT>
<DD>Integer constant
</DD>
</DL>
<H2>Description</H2>
<P>
   This constraint implements an arc-consistent version of X #= Y + C (i.e.
   any "holes" in the domain of X are propagated to Y and vice-versa).<P>

   A range error is thrown if X and Y do not have "reasonable" bounds
   (roughly +/- 2^30 on a 32-bit machine, roughly +/- 2^52 on a 64-bit
   machine: note that even much smaller bounds than this can lead to
   available memory being exhausted very rapidly, if not immediately).

<H2>See Also</H2>
<A HREF="../../lib/ic/HE-2.html">#= / 2</A>
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